In many heterogeneous catalytic reactions, especially those carried out at high temperature and high reaction rate such as selective oxidation reaction for syngas production, diffusion of reactants and/or products in the catalyst pores may affect the efficiency of catalyst material. Consequently, use of supports with small internal pores leads to inefficient use of catalyst because (i) the reactants do not have enough time to reach catalytic metals in the pores and (ii) the reactants may become trapped in the pores and interact in undesired secondary reactions during the diffusion of CO and H2 from the pores.
Accordingly, there is a continuing need for better, more economical processes and catalysts for the catalytic partial oxidation of hydrocarbons, particularly methane, or methane containing feeds, in which the catalyst retains a high level of activity and selectivity to carbon monoxide and hydrogen under conditions of high gas space velocity and elevated pressure.
Heterogeneous catalysts and or their supports are prepared with various methods, such as precipitation, with pore sizes rang from around 3–50 Å for zeolite catalysts to the order of micrometers for form and monolith catalysts. The pore sizes are often optimized to fit the application by adjusting the preparation procedure. For example, zeolite materials are generally synthesized through crystallization of silicon, aluminum, sodium, sodium hydroxide and an organic template (For details see Vaughan, D. E. W., The synthesis and manufacture of zeolites, Chem. Eng. Progr., 84(2), 25–31, 1988). The organic template, typically an organic amine or alkyl ammonium compound, works as molecular mold to generate the porous network. The template is then removed through oxidation.
Pore generation reagents, such as carbon, sulfur are used to increase the porosity of corresponding catalyst or its support. These reagents are mixed with the catalyst precursor and compressed to form the desired shape. Calcination of the shapes material to combust the carbon (e.g. graphite) or sulfur results in the formation of pores. Due to the low temperature of removing such reagent, the catalyst prepared in such a way typically do no have good thermal stability, due to the lack of high temperature treatment in its preparation.
In contrast to the prior art, this invention discloses a new method of using inorganic compound as template to prepare catalyst its support material with desired porosity and high thermal stability.